scholarly journals Surface structures of metallic monolayers on metal crystal surfaces

1979 ◽  
Vol 16 (6) ◽  
pp. 2073-2085 ◽  
Author(s):  
J. P. Biberian ◽  
G. A. Somorjai
Keyword(s):  
Surface Structures ◽  
Crystal Surfaces ◽  
Metal Crystal

SREM imaging of copper (110) vicinal surfaces

1989 ◽  
Vol 47 ◽  
pp. 542-543
Author(s):  
J. Liu ◽  
J. M. Cowley
Keyword(s):  
Copper Wire ◽  
Real Space ◽  
Surface Structures ◽  
Single Atom ◽  
Objective Lens ◽  
Vicinal Surface ◽  
Vicinal Surfaces ◽  
Crystal Surfaces ◽  
Copper Surfaces ◽  
Surface Areas

Scanning reflection electron imaging technique is sensitive to surface perturbations at nano-meter scale. Single atom high steps and defects on crystal surfaces can be observed with high contrast. Microanalysis of surface areas can be performed to study surface reaction problems. One advantage of SREM over conventional REM imaging is that by changing the objective lens current synchronously with the frame speed one can manage to keep more of the scanned areas in focus. This dynamic focusing is important for observing less flat surfaces such as the vicinal surface areas. We take this advantage to study the copper (110) vicinal surface structures by SREM technique. All the SREM images reported here are obtained with dynamic focusing conpensation. RHEED study of clean and oxygen adsorbed copper surfaces revealed that most of the vicinal surfaces will be faceted upon oxygen adsorption. Real space observations of these faceted surface areas by SREM imaging may yield some information about the vicinal surface structures with high resolution. The copper surfaces were obtained by melting copper wire in air with careful control to reduce high temperature oxidations on Ihe crystal surfaces. Reasonably flat copper crystal surfaces can be obtained by this preparation method and some of the surface areas are oxidized. The experiment was performed in a VG HB5 STEM instrument with a probe size of about 0.5 nm in diameter and a vacuum pressure of about 5×10-9 Torr.

scholarly journals The reactivity of low index [(111) and (100)] and stepped platinum single crystal surfaces

1972 ◽  
Vol 331 (1586) ◽  
pp. 335-346 ◽  
Keyword(s):  
Single Crystal ◽  
Surface Composition ◽  
Diatomic Molecules ◽  
Catalytic Reactions ◽  
Surface Structures ◽  
Crystal Surfaces ◽  
Small Surface ◽  
Stepped Surfaces ◽  
Platinum Surfaces ◽  
Platinum Single Crystal

Several high Miller index crystal surfaces of platinum have been shown to consist of low index (111) or (100) terraces of constant width, linked by steps of monatomic height. The surface structures that form in the presence of diatomic molecules (H 2 , O 2 , CO, NO), aliphatic and aromatic hydrocarbons on the (111), (100) and on these stepped platinum surfaces were studied by low energy diffraction. Several catalytic reactions (H 2 + D 2 ; H 2 + O 2 ; dehydrocyclization of n -heptane) that take place on the various platinum crystal surfaces at low pressures were monitored by means of a mass spectrometer and the surface composition by Auger electron spectroscopy. The chemisorption characteristics of diatomic molecules on stepped platinum surfaces are markedly different from those on low index [(111) and (100)] platinum surfaces. Organic molecules of different types form ordered surface structures on low index faces of platinum, but decompose rapidly on stepped surfaces under identical experimental conditions. Surface chemical reactions of diatomic molecules that were studied take place only on stepped surfaces at a detectable rate. The dehydrocyclization of n -heptane to toluene occurs slowly on the Pt(lll) face. The rate of decomposition of n -heptane on stepped platinum surfaces is rapid and the carbon deposit that forms prevents dehydrocyclization. In the presence of hydrogen, however, dehydrocyclization occurs at a rapid rate on stepped surfaces with atomic terraces of (111) orientation, while at a slower rate on stepped surfaces with atomic terraces of (100) orientation. It appears that catalytic reactions can readily be studied using one face of a single crystal of small surface area. Dissociation of diatomic molecules and breaking of C—C and C—H bonds occur preferentially at atomic steps, while the structure of the atomic terraces plays an important role in the more complex dehydrocyclization reaction.

Scanning and Transmission Microscopy of Nematocyst Batteries in Epitheliomuscular Cells of Hydra

1971 ◽  
Vol 29 ◽  
pp. 410-411 ◽  
Author(s):  
Jane A. Westfall ◽  
S. Yamataka ◽  
Paul D. Enos
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Osmium Tetroxide ◽  
External Surface ◽  
Three Dimensional ◽  
Surface Structures ◽  
Transmission Microscopy ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Scanning Electron

Scanning electron microscopy (SEM) provides three dimensional details of external surface structures and supplements ultrastructural information provided by transmission electron microscopy (TEM). Animals composed of watery jellylike tissues such as hydras and other coelenterates have not been considered suitable for SEM studies because of the difficulty in preserving such organisms in a normal state. This study demonstrates 1) the successful use of SEM on such tissue, and 2) the unique arrangement of batteries of nematocysts within large epitheliomuscular cells on tentacles of Hydra littoralis.Whole specimens of Hydra were prepared for SEM (Figs. 1 and 2) by the fix, freeze-dry, coat technique of Small and Màrszalek. The specimens were fixed in osmium tetroxide and mercuric chloride, freeze-dried in vacuo on a prechilled 1 Kg brass block, and coated with gold-palladium. Tissues for TEM (Figs. 3 and 4) were fixed in glutaraldehyde followed by osmium tetroxide. Scanning micrographs were taken on a Cambridge Stereoscan Mark II A microscope at 10 KV and transmission micrographs were taken on an RCA EMU 3G microscope (Fig. 3) or on a Hitachi HU 11B microscope (Fig. 4).

Electron-Mirror Microscopic Aspects of Ferroelectric Domains of BaTiO3 And Ca2Sr (C2H5CO2)6

1970 ◽  
Vol 28 ◽  
pp. 478-479
Author(s):  
Teruo Someya ◽  
Jinzo Kobayashi
Keyword(s):  
Surface Layer ◽  
Electric Fields ◽  
Quantitative Study ◽  
Recent Progress ◽  
Ferroelectric Domain ◽  
Resolving Power ◽  
Surface Pattern ◽  
Crystal Surfaces ◽  
One Dimensional ◽  
Ferroelectric Domains

Recent progress in the electron-mirror microscopy (EMM), e.g., an improvement of its resolving power together with an increase of the magnification makes it useful for investigating the ferroelectric domain physics. English has recently observed the domain texture in the surface layer of BaTiO3. The present authors ) have developed a theory by which one can evaluate small one-dimensional electric fields and/or topographic step heights in the crystal surfaces from their EMM pictures. This theory was applied to a quantitative study of the surface pattern of BaTiO3).

Electron Microscopic Observation of Biological Specimens in Their Native State by Employing Cryogenic Techniques

1972 ◽  
Vol 30 ◽  
pp. 410-411 ◽  
Author(s):  
Tokio Nei ◽  
Haruo Yotsumoto ◽  
Yoichi Hasegawa ◽  
Yuji Nagasawa
Keyword(s):  
Electron Microscopic Observation ◽  
Surface Structures ◽  
Specimen Preparation ◽  
Native State ◽  
Electron Microscopic ◽  
Biological Specimen ◽  
Specimen Holder ◽  
Cold Stage ◽  
Preparation Techniques ◽  
Scanning Electron

In order to observe biological specimens in their native state, that is, still containing their water content, various methods of specimen preparation have been used, the principal two of which are the chamber method and the freeze method.Using its recently developed cold stage for installation in the pre-evacuation chamber of a scanning electron microscope, we have succeeded in directly observing a biological specimen in its frozen state without the need for such conventional specimen preparation techniques as drying and metallic vacuum evaporation. (Echlin, too, has reported on the observation of surface structures using the same freeze method.)In the experiment referred to herein, a small sliced specimen was place in the specimen holder. After it was rapidly frozen by freon cooled with liquid nitrogen, it was inserted into the cold stage of the specimen chamber.

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